That means, either he was in on it or he was too dumb to see what was goin' on.
7 seconds sound clip from the Casino (1995) movie soundboard.
You can hear this line at 01:21:45 in the Blu-ray version of the movie.
Quote context
[...]
- Now friends vote. Family and money votes.
- That's important to me and you.
- And if you'll think about our little problem along them lines...
- And you'll forgive me for sayin' it maybe he did not deserve to be fired.
- That means, either he was in on it or he was too dumb to see what was goin' on.
- Either way, I cannot have a man like that working here.
- Before we point the dirty end of the stick at old Don we better be sure we can prove them charges.
- Believe me, if I could prove it, he would be under arrest.
- I think you're way out of line talking to me like that.
[...]